Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2010 Jan 4:11:3.
doi: 10.1186/1471-2474-11-3.

Modular titanium alloy neck adapter failures in hip replacement--failure mode analysis and influence of implant material

Thomas M Grupp  1 , Thomas Weik, Wilhelm Bloemer, Hanns-Peter Knaebel
Affiliations

Modular titanium alloy neck adapter failures in hip replacement--failure mode analysis and influence of implant material

Thomas M Grupp et al. BMC Musculoskelet Disord. .

Abstract

Background: Modular neck adapters for hip arthroplasty stems allow the surgeon to modify CCD angle, offset and femoral anteversion intraoperatively. Fretting or crevice corrosion may lead to failure of such a modular device due to high loads or surface contamination inside the modular coupling. Unfortunately we have experienced such a failure of implants and now report our clinical experience with the failures in order to advance orthopaedic material research and joint replacement surgery.The failed neck adapters were implanted between August 2004 and November 2006 a total of about 5000 devices. After this period, the titanium neck adapters were replaced by adapters out of cobalt-chromium. Until the end of 2008 in total 1.4% (n = 68) of the implanted titanium alloy neck adapters failed with an average time of 2.0 years (0.7 to 4.0 years) postoperatively. All, but one, patients were male, their average age being 57.4 years (36 to 75 years) and the average weight 102.3 kg (75 to 130 kg). The failures of neck adapters were divided into 66% with small CCD of 130 degrees and 60% with head lengths of L or larger. Assuming an average time to failure of 2.8 years, the cumulative failure rate was calculated with 2.4%.

Methods: A series of adapter failures of titanium alloy modular neck adapters in combination with a titanium alloy modular short hip stem was investigated. For patients having received this particular implant combination risk factors were identified which were associated with the occurRence of implant failure. A Kaplan-Meier survival-failure-analysis was conducted. The retrieved implants were analysed using microscopic and chemical methods. Modes of failure were simulated in biomechanical tests. Comparative tests included modular neck adapters made of titanium alloy and cobalt chrome alloy material.

Results: Retrieval examinations and biomechanical simulation revealed that primary micromotions initiated fretting within the modular tapered neck connection. A continuous abrasion and repassivation process with a subsequent cold welding at the titanium alloy modular interface. Surface layers of 10 - 30 microm titanium oxide were observed. Surface cracks caused by fretting or fretting corrosion finally lead to fatigue fracture of the titanium alloy modular neck adapters. Neck adapters made of cobalt chrome alloy show significantly reduced micromotions especially in case of contaminated cone connection. With a cobalt-chromium neck the micromotions can be reduced by a factor of 3 compared to the titanium neck. The incidence of fretting corrosion was also substantially lower with the cobalt-chromium neck configuration.

Conclusions: Failure of modular titanium alloy neck adapters can be initiated by surface micromotions due to surface contamination or highly loaded implant components. In the present study, the patients at risk were men with an average weight over 100 kg. Modular cobalt chrome neck adapters provide higher safety compared to titanium alloy material.

PubMed Disclaimer

Figures

Figure 1
Figure 1
X-ray of a hip with a failed neck.
Figure 2
Figure 2
Occurrence of clinical neck failures in a postoperative time period in months.
Figure 3
Figure 3
Correlation weight of patients and failures.
Figure 4
Figure 4
Kaplan-Meier survival analysis for failed neck adapter as reason of revision (± 95% confidence interval).
Figure 5
Figure 5
Metha Short Hip Stem System.
Figure 6
Figure 6
Test setup for measurement of micromotions in the modular cone connection (left) and particle-contaminated joining area (right) [18,19].
Figure 7
Figure 7
Test setup for neck test (left) and stem test (right) with reference electrode to measure corrosion potential.
Figure 8
Figure 8
Fatigue fracture surface of a clinically failed titanium neck adapter.
Figure 9
Figure 9
Metallographic analyses revealed microcracks on the cone surface (left) and a potential microcrack in a fretting area (right).
Figure 10
Figure 10
Overview of interface characteristics and time to failure of the retrievals.
Figure 11
Figure 11
Brittle layer in cone connection between stem and neck adapter.
Figure 12
Figure 12
Retrieved faultless titanium alloy neck adapter (left) and stem (right) without contamination and any signs of corrosion.
Figure 13
Figure 13
Settling behaviour of a clean titanium alloy neck adapter (left) and a particle-contaminated joining (right) [18].
Figure 14
Figure 14
Micromotions in a clean and particle-contaminated interface (Mean ± STD) for titanium and cobalt-chromium alloy neck adapters (medial and lateral).
Figure 15
Figure 15
Endurance behaviour of the modular stem and different failure mechanisms for neck components made of titanium (failure of the neck adapter) and of cobalt-chromium alloy (fractured stem at a level below the embedding).
Figure 16
Figure 16
Free redox potential with frequent repassivation processes in the particle-contaminated modular neck interface (red curve) compared with a clean joining (blue curve).
See this image and copyright information in PMC

References

    1. Toni A, Paderni S, Sudanese A, Guerra E, Traina F, Antonietti B, Giunti A. Anatomic cementless total hip arthroplasty with ceramic bearings and modular necks: 3 to 5 years follow-up. Hip International. 2001;11(1):1–17. - PubMed
    1. Traina F, Baleani M, Viceconti M, Toni A. Modular Neck Primary Prosthesis: Experimental and Clinical Outcomes. Scientific Exhibit at the 71st AAOS Annual Meeting, San Francisco. 2004.
    1. Toni A, Sudanese A, Paderni S, Guerra E, Bianchi G, Antonietti B, Giunti A. Artroprotesi d'anca non cementata con collo modulare - Cementless hip arthroplasty with a modular neck. Chir Organi Mov. 2001;LXXXVI:73–85. - PubMed
    1. Braun A, Lazovic D, Zigan R. Modular short stem prosthesis- Implant positioning and the impact of navigation. Orthopedics Suppl. 2007;30(Suppl 10):144–147. - PubMed
    1. Keggi KJ. My experience with proximal modular stems. Symposium "Cutting-edge developments on proximal modularity in THA" Annual AAHKS Meeting. 2008. pp. 16–22.

MeSH terms